Radiation curable hardcoat compositions possessing anti-fog properties

ABSTRACT

Transparent substrates are rendered resistant to fogging by the application of a hardcoat composition comprising finely divided silica, a multi-functional olefin containing two or more olefinic moieties and one or more divalent oxyalkylene radicals having the formula: 
     
         --((CX2).sub.n O).sub.x ((CX2)O).sub.y -- 
    
     where the sum of the x stoichiometric subscripts for each divalent oxyalkylene radical and the sum of the y stoichiometric subscripts for each divalent oxyalkylene radical when said sums are added together is ten or greater and the stoichiometric subscripts n and m are different and have values independently ranging from one to ten, where each X is independently selected from the group consisting of hydrogen, one to forty carbon atom monovalent hydrocarbon radicals and six to forty carbon atom monovalent aromatic hydrocarbon and an olefinically functionalized trialkoxysilane followed by curing.

FIELD OF THE INVENTION

The present invention relates to a hardcoat composition for transparentthermoplastics that is radiation or electron beam curable comprisingsilicon and a polyacrylate comprising an oxyalkylene moiety whereby thehardcoat exhibits resistance to fogging under exposure to moist air.

BACKGROUND OF THE INVENTION

Transparent thermoplastics have replaced glass in many applications,e.g. transportation glazing, taillight and headlight lenses, correctiveoptical lenses, architectural glazing and the like. Transparentthermoplastic polymers are lighter and more shatter resistant thanglass. Consequently, the use of transparent thermoplastics intransportation glazing leads to a reduction in vehicular weight whichleads to an improved fuel economy. Further, the improved shatterresistance of the transparent thermoplastic imparts additional improvedsafety features when accidents occur that would normally shatter glassglazing or lenses.

However, transparent thermoplastics are not as hard as glass andconsequently these materials have a tendency to scratch and mar witheven ordinary use due to dust, contact with abrasives, cleaningequipment and weathering. Continuous scratching or marring results inreduced visibility or transparency of the material defeating its initialpurpose. This leads to the need to replace the material. In fact, onewidely used transparent thermoplastic, polycarbonate, is so soft in anuntreated or uncoated state that soft paper tissues can scratch thesurface. Since this material has received widespread application as areplacement material for eyeglass lenses, this can be a significantdrawback.

There thus has developed a significant body of technology dealing withmeans of coating transparent thermoplastics, thereby producingtransparent laminates, to improve their performance characteristics tobe more similar to that of glass while at the same time retaining theweight advantages that the less dense thermoplastics intrinsicallypossess. U.S. Pat. No. 4,348,462 discloses a radiation curable hardcoatcomposition for such transparent thermoplastics that comprises colloidalsilica, an acryloxysilane, and a non-silyl acrylate. This composition,as a coating, imparts improved abrasion resistance to transparentthermoplastics relative to the same thermoplastics that are not socoated, thus the term hardcoat. These generic formulations have beencontinuously improved but even recent U.S. patents still recitecolloidal silica, an alkoxy silylacrylate (cf. acryloxysilane), and areactive acrylic monomer (U.S. Pat. No. 5,468,789). Alternativeformulations recite colloidal silica and a multi-functional acrylate(U.S. Pat. No. 5,075,348), which is primarily a diacrylate species.

While these compositions impart a certain hardness to the coating byvirtue of the presence of the colloidal silica, which on a micro-scalecould be assumed to mimic glass, the matrix binding the colloidal silicawithin the coating and also binding the coating to the transparentthermoplastic substrate is an organic polymer having a tendency to behydrophobic.

As a hydrophobic coating, colloidal silica dispersed in a polymerizedorganic matrix such as an acrylate does not function well in moistenvironments. When exposed to water, either as rain, fog, mist or ahumid atmosphere, condensation occurs on the surface of the transparentthermoplastic and the water tends to bead up. The phase boundary of thewater beads on the surface of the transparent thermoplastic serves toreflect and refract light, which is undesirable. Further, water istransparent and has a different index of refraction from the transparentthermoplastic substrate, the beads of water on the surface display alensing effect interfering with visibility. Thus, a hydrophilic coatinghaving anti-fog, that is anti-beading properties for water, would havebetter optical properties when challenged by water. This is because asthe hydrophilicity of the surface coating increased, condensed water onthe surface would have an increasing tendency to form a sheet instead ofa multiplicity of water droplets that interfered with visibility ortransmission of light.

While anti-fog coatings are known, and have been used with sometransparent thermoplastics, they have not been particularly abrasionresistant (U.S. Pat. No. 3,933,407). The anti-fog coatings disclosed inU.S. Pat. No. 3,933,407 were applied to flexible polyethylene films aswell as to rigid articles manufactured from glass and transparentthermoplastics. However, these coatings were not particularly abrasionresistant, i.e. they contained no colloidal silica.

SUMMARY OF THE INVENTION

We now disclose radiation curable hardcoat compositions that haveimproved resistance to fogging.

The present invention provides for an ultraviolet curable hardcoatcomposition comprising:

(A) finely divided silica:

(B) a multi-functional olefin containing two or more olefinic moietiesand one or more divalent oxyalkylene radicals having the formula:

    --((CX.sub.2).sub.n O).sub.x ((CX.sub.2).sub.m O).sub.y --

where the sum of the x stoichiometric subscripts for each divalentoxyalkylene radical and the sum of the y stoichiometric subscripts foreach divalent oxyalkylene radical when said sums are added together isten or greater and the stoichiometric subscripts n and m are differentand have values independently ranging from one to ten, where each X isindependently selected from the group consisting of hydrogen, one toforty carbon atom monovalent hydrocarbon radicals and six to fortycarbon atom monovalent aromatic hydrocarbon radicals; and

(C) an olefinically functionalized trialkoxy silane.

The present invention also provides a method for making an ultravioletcurable hardcoat composition comprising:

(a) reacting

(i) an olefinically functionalized trialkoxy silane with

(ii) a finely divided silica in the presence of

(iii) a hydroxylic solvent to produce a reaction product and

(b) mixing the reaction product with a multi-functional olefincontaining two or more olefinic moieties and one or more divalentoxyalkylene radicals having the formula:

    --((CX.sub.2).sub.n O).sub.x ((CX.sub.2).sub.m O).sub.y --

where the sum of the x stoichiometric subscripts for each divalentoxyalkylene radical and the sum of the y stoichiometric subscripts foreach divalent oxyalkylene radical when said sums are added together isten or greater and the stoichiometric subscripts n and m are differentand have values independently ranging from one to ten, where each X isindependently selected from the group consisting of hydrogen, one toforty carbon atom monovalent hydrocarbon radicals and six to fortycarbon atom monovalent aromatic hydrocarbon radicals.

The present invention further provides a method for making a laminatecomprising:

(a) reacting

(i) an olefinically functionalized trialkoxy silane with

(ii) a finely divided silica in the presence of

(iii) a hydroxylic solvent to produce a reaction product and

(b) mixing the reaction product with a multi-functional olefincontaining two or more olefinic moieties and one or more divalentoxyalkylene radicals having the formula:

    --((CX.sub.2).sub.n O).sub.x ((CX.sub.2).sub.m O).sub.y --

where the sum of the x stoichiometric subscripts for each divalentoxyalkylene radical and the sum of the y stoichiometric subscripts foreach divalent oxyalkylene radical when said sums are added together isten or greater and the stoichiometric subscripts n and m are differentand have values independently ranging from one to ten, where each X isindependently selected from the group consisting of hydrogen, one toforty carbon atom monovalent hydrocarbon radicals and six to fortycarbon atom monovalent aromatic hydrocarbon radicals thereby preparingan ultraviolet curable hardcoat composition; and

(c) applying the ultraviolet curable hardcoat composition to atransparent substrate.

In addition the present invention provides a method for rendering atransparent substrate resistant to fogging comprising:

(a) reacting

(i) an olefinically functionalized trialkoxy silane with

(ii) a finely divided silica in the presence of

(iii) a hydroxylic solvent to produce a reaction product and

(b) mixing the reaction product with a multi-functional olefincontaining two or more olefinic moieties and one or more divalentoxyalkylene radicals having the formula:

    --((CX.sub.2).sub.n O).sub.x ((CX.sub.2).sub.m O).sub.y --

where the sum of the x stoichiometric subscripts for each divalentoxyalkylene radical and the sum of the y stoichiometric subscripts foreach divalent oxyalkylene radical when said sums are added together isten or greater and the stoichiometric subscripts n and m are differentand have values independently ranging from one to ten, where each X isindependently selected from the group consisting of hydrogen, one toforty carbon atom monovalent hydrocarbon radicals and six to fortycarbon atom monovalent aromatic hydrocarbon radicals thereby preparingan ultraviolet curable hardcoat composition;

(c) applying the ultraviolet curable hardcoat composition to atransparent substrate; and

(d) curing the ultraviolet curable hardcoat composition.

DETAILED DESCRIPTION OF THE INVENTION

The hardcoat composition of the present invention is a radiation orelectron beam curable composition that may be coated onto a substrate toimpart both abrasion resistance and anti-fogging properties to thematerial coated (the phrase ultraviolet curable in the appended claimsincludes curing processes that occur by means of free radicalprocesses). The primary use envisioned for the coating composition ofthe present invention is to coat transparent thermoplastics that arenormally soft and easily scratched by comparison to glass. While coatingglass with the composition of the present invention might notparticularly improve the abrasion resistance of the glass, it isconceivable that the coating could improve the anti-foggingcharacteristics of the glass so coated, a benefit to automotive glazingand architectural glazing applications. Thus the term transparentsubstrate in the appended claims includes glass. The term transparentthermoplastic includes but is not limited to polycarbonates,polyacrylates, polymethylmethacrylates, polystyrenes, polyolefins suchas polyethylene, polypropylene, syndiotactic crystalline polypropylene,polyesters such as polyethylene terephthalate and polybutyleneterephthalate, styrene acrylonitrile copolymers, polyamides such asnylon, polyimides and the various copolymers of these materials. Forpurposes of definition, any transparent polymeric material that isthermoplastic and possesses an ASTM D871 haze below about 200 (or anequivalent ASTM measurement since D871 is actually used to measure theturbidity of solutions) through an optical path of 5 mm is defined as atransparent thermoplastic.

The anti-fogging hardcoat compositions of the present inventioncomprise:

(A) from about 0.3 weight percent to about 35.0 weight percent,preferably from about 1.5 weight percent to about 24.0 weight percent,more preferably from about 4.5 weight percent to about 18.0 weightpercent and most preferably from about 8.0 weight percent to about 15.0weight percent of finely divided or colloidal silica, having an averageparticle size ranging from about 5 to about 40 nanometers, preferablyfrom about 10 to about 30, more preferably from about 15 to about 25,and most preferably from about 16 to about 22 nanometers in diameter.When supplied as colloidal silica, the finely divided silica will besupplied as a colloidal dispersion in a solvent, typically water, or amixture of water and a water miscible alcohol. Since the compositions ofthe present invention are made and used as coatings, a liquid vehicle istypically necessary to render the composition coatable. Due to thenature of the other components, water or a mixture of water and watermiscible solvents is generally used, a particularly preferred class ofwater miscible solvents is alcohols.

(B) from about 20.0 weight percent to about 97.0 weight percent,preferably from about 40.0 weight percent to about 95.0 weight percent,more preferably from about 50.0 weight percent to about 92.0 weightpercent and most preferably from about 60.0 weight percent to about 90.0weight percent a di- or multi-functional alkenyl compound wherein thealkenyl functionalities of the molecule are separated by oralternatively joined by at least one divalent polyoxyalkylene moietyhaving the formula:

    --((CX.sub.2).sub.n O).sub.x (CX.sub.2).sub.m O).sub.y --

where the sum of x+y is ten or greater, n≠m, and n and m have valuesranging from one to ten, preferably from one to eight, more preferablyfrom one to seven, and most preferably from one to five where each X isindependently selected from the group consisting of hydrogen, one toforty carbon atom monovalent hydrocarbon radicals and six to fortycarbon atom monovalent aromatic hydrocarbon radicals, the alkenylfunctionalities being joined to the divalent oxyalkylene moiety by amonovalent, divalent, or multivalent alkylene moiety whereby the alkenylcompound is rendered di-, tri-, or multi-functional in terms of olefinicunsaturation. Preferably X is hydrogen, a one to ten carbon atommonovalent hydrocarbon radical or a six to ten carbon atom monovalentaromatic radical, more preferably X is hydrogen or methyl, and mostpreferably X is hydrogen. The term hydrocarbon radical is defined toinclude, but is not limited to, for example alkyl, alkenyl, alkynyl,hydroxy-alkyl, halo-alkyl, amino-alkyl, thio-alkyl, aryl, phenyl,benzyl, pyridinyl, thiophenyl, furanyl, naphthyl, anthracenyl and othercondensed ring aromatics and condensed ring heterocycles where thehetero atom may be oxygen, nitrogen, sulfur or phosphorus.

The monovalent alkylene moiety is defined as a radical having theformula:

    CH.sub.2 ═CH--R--

where R is any divalent atom or radical; the divalent alkylene moietyhas the formula:

    CH.sub.2 ═CH--R.sup.1 <

where R¹ is any trivalent atom or radical; the trivalent alkyleneradical has the formula: ##STR1## where R² is any tetravalent atom orradical. By appropriate use of the di- and trivalent alkylene radicals amulti-functional alkylene compound may be assembled. For purposes ofdefinition, particular examples of divalent atoms are O, S, Se andnon-metals having a (-2) oxidation state as well as those metals andnon-metals having a (+2) oxidation state. Similarly, for purposes ofdefinition, particular examples of trivalent atoms are N, P, As, Sb andnon-metals having a (-3) oxidation state as well as those metals andnon-metals having a (+3) oxidation state. Finally, for purposes ofdefinition, particular examples of quadrivalent atoms are C, Si, Ge, Snand non-metals having a (-4) oxidation state as well as those metalshaving a (+4) oxidation state.

Divalent radicals are defined as any collection of two or more atomssatisfying the rules of chemical combination but having two unsatisfiedpoints of chemical bonding so that they may be incorporated into thestructure thereby satisfying the rules of chemical bonding. Examples ofdivalent species subtended by this description are: --(CH₂)_(p) -- wherep may range from 1 to numbers as large as 40, --CH═CH--, H₂ C═C<,--C.tbd.C--, --CO₂ --, --C₆ H₄ -- (divalent phenyl), --C₆ H₁₀ --(divalent cyclohexyl), and the like. It should be noted that two or moredivalent radicals or atoms may joined one to the other thereby creatinganother divalent radical which will function in like manner in terms ofchemical structure and bonding.

Trivalent radicals are defined as any collection of two or more atomssatisfying the rules of chemical combination but having threeunsatisfied points of chemical bonding so that they may be incorporatedinto the structure thereby satisfying the rules of chemical bonding.Examples of trivalent species subtended by this description are:##STR2## where q may range from 1 to numbers as large as 40, --C₆ H₃ ═(trivalent phenyl), --C₆ H₉ ═ (trivalent cyclohexyl), and the like. Itshould be noted that divalent atoms or radicals may be combined with atrivalent atom or radical to create additional trivalent radicals. Thecombination of two or more trivalent atoms or radicals with one or moredivalent atom or radical creates a multivalent radical.

The structural combinations and permutations subtended by thisdescription are fairly large. In order for the compositions of thepresent invention to function as an ultraviolet or electron beam curablecompositions that impart anti-fogging properties to a hardcoat, the di-or multi-functional alkenyl compound must possess at least one divalentpolyoxyalkylene moiety having the formula:

    --((CX.sub.2).sub.n O).sub.x ((CX.sub.2).sub.m O).sub.y --

where the sum of x+y is ten or greater, n≠m, and n and m have valuesranging from one to ten, preferably from one to eight, more preferablyfrom one to seven, and most preferably from one to five where each X isindependently selected from the group consisting of hydrogen, one toforty carbon atom monovalent hydrocarbon radicals and six to fortycarbon atom monovalent aromatic hydrocarbon radicals and two or moreolefinic moieties having a structural formula: ##STR3## where theunsatisfied points of chemical bonding are satisfied by divalent,trivalent or quadrivalent atoms or radicals or terminated by monovalentatoms or radicals, the monovalent atoms being selected from the groupconsisting of hydrogen, the halogens fluorine, chlorine, bromine, andiodine, monovalent hydrocarbon radicals having from one to forty carbonatoms and monovalent aromatic hydrocarbon radicals having from six toforty carbon atoms. The multi-functional olefin must contain at leasttwo olefinic moieties and at least one oxyalkylene divalent radicalchemically linked by some combination of divalent, trivalent, andquadrivalent atoms or radicals with termination of unsatisfied points ofchemical bonding by monovalent atoms or radicals. When the di- ormulti-functional alkenyl compound possesses more than onepolyoxyalkylene moiety, e.g. --((CX2)_(n) O)_(x)(i) ((CX2)_(m) O)_(y)(j)--, --((CX2)_(n) O)_(x)(ii) ((CX2)_(m) O)_(y)(jj) --, ((CX2)_(n)O)_(x)(iii) ((CX2)_(m) O)_(y)(jjj) --, . . . , the sum of thestoichiometric subscripts x (x(i)+x(ii)+x(iii)+ . . . ) and y(y(j)+y(jj)+y(jjj)+ . . . ) must be ten or greater. Thus chain length ofthe polyoxyalkylene bridge in the di- or multi-functional alkenylcompound may be shortened if the number of divalent polyoxyalkylenebridging groups present in the molecule is increased, with X aspreviously defined.

Another formula for the di- or multi-functional alkenyl compound isthus:

    J.sub.2 C═CJQ((CH.sub.2).sub.n O).sub.x ((CH.sub.2).sub.m O).sub.y QJC═CJ.sub.2

where Q is independently selected from the group of divalent, trivalentand tetravalent atoms and radicals subject to the limitation that iftrivalent or tetravalent atoms or radicals are selected the unsatisfiedpoints of chemical bonding are satisfied by a monovalent atom orradical, and J is selected from the group of monovalent, divalent,trivalent and quadrivalent atoms or radicals subject to the limitationthat if divalent, trivalent or tetravalent atoms or radicals areselected the unsatisfied points of chemical bonding are satisfied by amonovalent atom or radical. The purpose of the foregoing is todemonstrate the multiplicity of structures that will satisfy the minimumrequirements that the compound be di- or multi-functional in respect tothe number of points of olefinic unsaturation possessing at least onelong oxyalkylene chain as defined by the subscripts n and m. While itmay not be possible to write a perfectly generalizable formula for adi-olefin that contains at least one oxyalkylene moiety the previousexposition is by way of explaining the structural variations that arepossible to meet this minimum requirement. Consequently while theappended claims may recite simpler species that satisfy this minimumrequirement, all compounds that satisfy this minimum requirement byvirtue of such structural variations and permutations are included.Applicants note that two embodiments satisfying the requirements forcomponent (B) of the compositions of the present invention are availablecommercially, SR610 and SR295, from Sartomer of Extort, Pa. Otherembodiments satisfying the structural requirements of component (B) maybe conveniently synthesized using the techniques of organic synthesisknown in the art and science of organic chemistry.

One particularly useful sub-class of this large class of materials is:##STR4## in particular where n=2, m=0, x=13, y=0; where the di-olefin isa diacrylate. In this particular example, the alkylene moiety is H₂C═CH--, J is hydrogen, and Q is a divalent radical, R, which has nobranching points for further substituents, ##STR5## The example thusminimally satisfies the requirement that the di- or multi-functionalolefin (used interchangeably with di- or multi-functional alkylenecompound) should have at least one oxyalkylene (used interchangeablywith polyoxyalkylene) divalent radical.

(C) from about 0.1 weight percent to about 40.0 weight percent,preferably from about 0.5 weight percent to about 30.0 weight percent,more preferably from about 1.0 weight percent to about 20.0 weightpercent and most preferably from about 2.0 weight percent to about 10.0weight percent of an olefinically functionalized trialkoxy silane havingthe general formula:

R₄ Si(OR³)₃, where R⁴ is a monovalent alkylene radical having from twoto forty carbon atoms and R³ is selected from the group of one to fortycarbon atom monovalent alkyl hydrocarbon radicals and six to fortycarbon atom monovalent aromatic hydrocarbon radicals. A more specificformula for the olefinically functionalized trialkoxy silane is asfollows: ##STR6## where J' is selected from the group of previouslydefined monovalent, divalent, trivalent and quadrivalent atoms orradicals subject to the limitation that if divalent, trivalent ortetravalent atoms or radicals (or some combination thereof) are selectedthe unsatisfied points of chemical bonding are satisfied by a monovalentatom or radical; Q' is selected from the group of previously defineddivalent, trivalent and tetravalent atoms and radicals subject to thelimitation that if trivalent or tetravalent atoms or radicals areselected the unsatisfied points of chemical bonding are satisfied by amonovalent atom or radical and R³ is selected from the group of one toforty carbon atom monovalent alkyl hydrocarbon radicals and six to fortycarbon atom monovalent aromatic hydrocarbon radicals.

A particularly preferred example of component (C) is the following:##STR7##

Molecules having the general formula, R'Si(OR")₃ (cf. R⁴ Si(OR³)₃), aremonomeric precursors to T resins because they are susceptible toreaction with hydroxylic solvents. By hydroxylic solvent is meant water,alcohols, Bronsted acids or mixtures of these and the like which willinitiate solvolysis. The solvolysis of T resin precursors in hydroxylicsolvents leads to a reaction known as polycondensation resulting in theT resin. Depending on the extent of the reactions, the product may ormay not be fully hydrolyzed and condensed. As generally used in thefield of ultraviolet curable coatings, such reactive T resin precursorswhen dissolved in a hydroxylic solvent such as water may be referred toas hydrolyzates, i.e. the hydrolysis and polycondensation product of a Tresin precursor dissolved in water or other hydroxylic solvent. As usedin the experimental section of the instant application, hydrolyzaterefers to the complex reaction mixture resulting when a T resinprecursor is mixed with aqueous colloidal silica. It is to be noted thatsuch a complex mixture may contain other additional polymerizablespecies that have been subsequently added, e.g., diacrylates such ashexanediol diacrylate.

Similar reactions occur in alcoholic solution (and other proticsolvents), although probably not at the same kinetic rate due to themuch lower reactivities of alcohols by comparison to that of water.Assuming a complete hydrolysis and polycondensation reaction, 100 partsby weight of methacryloxypropyltrimethoxy silane yields approximately 72parts by weight of methacryloxy propyl silsesquioxane as the fullyhydrolyzed and condensed reaction product of the methacryloxy propyltrimethoxy silane.

It is to be noted that the colloidal silica, component (A), is usuallyfurnished to the compositions of the present invention as an aqueousdispersion, which satisfies the requirement that a hydroxylic solvent bepresent. Component (C), an olefinically functionalized trialkoxy silane,as previously noted, is water reactive. Mixture of component (A), as anaqueous or alcoholic dispersion, with component (C) will functionalizethe finely divided (or colloidal) silica of component (A) and produce ahydrolyzate that is the polycondensation product of component (C) thatis in intimate mixture with the finely divided silica by reason of thewater (hydroxylic solvent) reactivity of component (C). In the casewhere the silica is furnished in an alcoholic dispersion, a small amountof water must be added to hydrolyze the alkoxy groups (or halide groups)present in the alkenyl hydrolyzable silane, component (C). Thus therecitation of a composition comprising curable or reactive species,e.g., components (A), (B), and (C) or components (A) and (C); in theappended claims also includes the reaction products thereof and mixturesof those reaction products. Applicants note that (B) and (C) can also beco-reactive if either one of the these two components are present insolution in a hydroxylic solvent and mixed together.

The compositions of the present invention may optionally include otherpolymerizable species as well. Such species may be mono-functionalolefins, e.g., acrylic acid or esters thereof, or acetylenes, e.g.,mono-butynylmaleate or fumarate. They may also be di- ormulti-functional such as the diacrylates. A particularly preferreddiacrylate is hexanediol diacrylate as an additional polymerizablecomponent. When such additional polymerizable components are used theyare added to the base composition containing components (A), (B), and(C) are used at a level of from about 2.9 weight percent to about 23.1weight percent, preferably from about 4.7 weight percent to about 16.6weight percent, and more preferably from about 7.4 weight percent toabout 12.2 weight percent. These ranges may be expressed as parts byweight per hundred parts by weight (pph) of the sum of (A), (B) and (C);thus 2.9 weight percent is approximately 3 pph, 23.1 weight percent isapproximately 30 pph, 4.7 weight percent is approximately 5 pph, 16.6weight percent is approximately 20 pph, 7.4 weight percent isapproximately 8 pph and 12.2 weight percent is approximately 14 pph.

Since the compositions of the present invention involve reactivemixtures of polymerizable species it is frequently desirable to includeolefin polymerization inhibitors at a weight level (on the totalcomposition) of from about 0.0001 weight percent to about 1.50 weightpercent, preferably from about 0.001 weight percent to about 1.00 weightpercent, more preferably from about 0.005 weight percent to about 0.50weight percent and most preferably from about 0.01 weight percent toabout 0.25 weight percent.

These olefin polymerization inhibitors may be selected from the groupconsisting of 2,6-di-tert-butyl-4-methyl-phenol,2-tert-butyl-4-methoxyphenol, 3-tert-butyl-4-methoxyphenol, alkylsubstituted phenol where the alkyl group has from 1 to 30 carbon atoms,di-alkyl substituted phenol where each alkyl group independently hasfrom one to 30 carbon atoms, tri-alkyl substituted phenol where eachalkyl group independently has from one to 30 carbon atoms, styrylphenol,di-styrylphenol, tri-styrylphenol,2,2'-methylenebis(4-methyl-6-tert-butylphenol),2,2'-methylenebis(4-ethyl-6-tert-butylphenol),4,4'-methylenebis(2,6-di-tert-butylphenol),2,2'-ethylidenebis(4,6-di-tert-butylphenol),2,2'-methylenebis(4-methyl-6-(1-methylcyclohexyl)-phenol),4,4'-butylidenebis(6-tert-butyl-3-methylphenol),4,4'-thiobis(6-tert-butyl-3-methylphenol),4,4'-methylenebis(2,6-dimethylphenol), 1,1'-thiobis(2-naphthol),2,2'-thiobis(4-methyl-6-tert-butylphenol),2,2'-isobutylidenebis(4,6-dimethylphenol), tetrakis(methylene3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate)methane,1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-benzene,1,3,5,-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-s-triazine-2,4,6(1H,3H,5H)trione,2,4-bis(n-octylthio)-6-(4-hydroxy-3,5-di-tert-butylamino)1,3,5-triazine, 4-(hydroxymethyl)-2,6,-di-tert-butylphenol,2,2-diphenyl-1-picrylhydrazyl, dilauryl thiodipropionate, distearylthiodipropionate,O,O-di-normal-octadecyl(3,5-di-tert-butyl-4-hydroxybenzyl)-phosphonate,1,6-hexamethylene bis(3,5-di-tert-butyl-4-hydroxyphenyl)propionate,thiodiethylene bis(3,5-di-tert-butyl-4-hydroxyphenyl)propionate,octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate,N,N'-hexamethylenebis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionamide,1,3,5-tris(2-hydroxyethyl)-s-triazine-2,4,6-(1H,3H,5H) trione,N-(4-hydroxyphenyl)butyramide, N-(4-hydroxyphenyl)pelargonamide,N-(4-hydroxyphenyl)dodecanamide, N-(4-hydroxyphenyl)stearamide,2,6-di-tert-butyl-4-(dimethylaminoethyl)phenol,1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl-s-triazine-2,4,6-(1H,3H,5H)trione, nickelbis(O-ethyl(3,5-di-tert-butyl-4-hydroxybenzyl)phosphonate),2,2'-oxamidobisethyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate,tris(2-tert-butyl-4-(2-methyl-4-hydroxy-5-tert-butylphenylthio)-5-methyl)phenylphosphite,tetrakis (2,4-di-tert-butylphenyl) 4,4'-diphenylylenediphosphonite,normal-propyl 3,4,5-tri-hydroxybenzoate, calciumbis(O-ethyl(3,5-di-tert-butyl-4-hydroxybenzyl)phosphonate, Banfield'sradical, 1,3,5-triphenyl verdazyl, Koelsch's radical,1-nitroso-2-naphthol, 4-hydroxy-2,2,6,6-tetramethyl-1-piperidin-1-oxyl,galvinoxyl, 2,5-di-tetramylhydroquinone, tert-butylhydroquinone, andmethylhydroquinone.

The following compounds have been referred to in this specification andunder the condition that the name referred to in the specification isnot sufficiently specific are hereby defined by Applicants by theirchemical structures as follows: ##STR8## where R is hydrogen for Tinuvin770®, and for other inhibitors carrying the same tradename but differentidentifying numbers, R may be selected from the group consisting ofhydrogen, monovalent hydrocarbon radicals of from one to about thirtycarbon atoms and monovalent alkoxyl groups where the alkyl of thealkoxyl is a monovalent hydrocarbon radical of from one to about thirtycarbon atoms; ##STR9##

The compositions of the present invention are ultraviolet or electronbeam curable. Frequently it is desirable to include in the composition aphoto-initiator to accelerate the speed of the ultraviolet cure. Severalcompounds are commercially available for this purpose, e.g.2-hydroxy-2-methyl-1-phenylpropan-1-one, available commercially asDarocur™ 1173 from Radcure of Smyrna, Ga.

The incorporation of colloidal silica into an ultraviolet or electronbeam curable coating composition that contains a di- or multi-functionalalkenyl compound that contains at least one oxyalkylene moiety rendersthe composition both anti-fogging and abrasion resistant.

Coating thickness of the compositions of the present invention may becontrolled by diluting the composition with water or with suitable watermiscible alcohols or mixtures thereof. It is also possible to use otherwater miscible organic compounds, e.g. acetone. Water miscible alcoholsare usually low molecular weight alcohols and are particularly usefulfor diluting these compositions, particularly alcohols having from oneto ten carbon atoms, preferably from two to eight carbon atoms, morepreferably from three to eight carbon atoms and most preferably fromthree to six carbon atoms. The alcohols may be mono-functional,di-functional as in ethylene glycol, or multi-functional.

The appended examples are include by reference to demonstrate thepractice of the present invention and are not intended by way ofdemonstration to construe any limitation on the appended claims.

All U.S. patents referenced herein, are herewith and hereby incorporatedby reference.

EXPERIMENTAL

Fogging Test

The fogging test referred to in the following examples is conducted asfollows. A beaker is filled to within one inch of the top with water andmaintained at a temperature of 50 ° C. Treated panels of transparentsubstrate are placed, treated face down on the beaker, and the timeuntil the appearance of condensate (fog) on the treated surface d thepanel (nearest the heated water) is measured. This time measurementusually ranges from less than one second to several seconds. Generally,the fogging times as measured by this test are accurate to ±1 second. Acoating (or hardcoating) that has a fogging time of 10±1 seconds orgreater is defined as anti-fogging.

Taber Haze (ASTM D-1044)

The ASTM test protocol leaves the auxiliary weight and the abradingwheel unspecified. These tests were conducted with that weight being 500g per wheel using CS-10F wheels.

EXAMPLE 1

A coating composition was prepared from the following ingredients:

1) 100 g of aqueous colloidal silica, having an average particle size of20±4 nanometers and 34 weight percent silica (component (A), Nalcoag1034A™);

2) 100 g of CH₂ ═CHC(O)O--(CH₂ CH₂ O)_(x) --OC(O)CH═CH₂, where xaverages approximately 13, available commercially as SR610™ fromSartomer d Exton, Pa. (component (B)); and

3) 12 g of 2-hydroxy-2-methyl-1-phenylpropan-1-one, availablecommercially as Darocur™ 1173 from Radcure of Smyrna, Ga. The resultingmixture was diluted with 160 g iso-propyl alcohol and thoroughly mixedby shaking. The mixture had a viscosity of 9 centipoise at 25° C.

Polyethylene terephthalate (PET) film was flow coated with this mixtureand allowed to air dry for approximately 30 minutes. The flow coatedfilm was subjected to ultraviolet radiation to initiate curing by twopasses through a Fusion System processor two inches from the 300 W/in²Fusion-H lamps, at a processing speed of 30 fpm.

The coating had a thickness of 9 microns and a fogging time of 20seconds. The change in Taber haze (ASTM D-1044) of the coating after 100cycles was 26%, in comparison to the uncoated PET film which experienceda change of 49% in Taber haze.

EXAMPLE 2

The mixture of example 1 was diluted with iso-propyl alcohol on a weightbasis of 2.8 parts alcohol to 1 part mixture. This coating compositionwas applied to PET film as in the previous example and after a flashtime of 20 seconds was cured in one pass at a processing speed of 50fpm. The resulting coating was 5 microns thick and had a fogging testtime in excess of 10 seconds (a pass) with a delta Taber haze of 32%.

EXAMPLE 3

In an Erlenmyer flask equipped with a magnetic stirring bar was added121.7 g of iso-propyl alcohol, 86.9 g, Nalcoag 1034A™, aqueous colloidalsilica (34 weight percent silica) and 0.07 g 4-OH TEMPO. To this mixturewas added 13.0 g methacryloxypropyltrimethoxy silane. The mixture washeated to reflux, approximately 80° C., for two hours and was thencooled to room temperature. 36.2 g of hexanediol diacrylate and 325 giso-propyl alcohol was then added. This mixture was then vacuum strippedat 10-20 torr on a rotary evaporator until no more overhead wascollected. Seventy-five grams of material was recovered that had acomposition as follows: silica (29.5 g), hexanediol diacrylate (36.2 g),and 9.4 g methacyloxypropyl silsesquioxane (acrylate functional Tresin).

To 33 g of the mixture containing silica, hexanediol diacrylate andacrylate functional T resin was added 67 g of ##STR10## available asSR9035™ from Sartomer of Exton, Pa., where each x(i) averages 5 and thesum of x(1)+x(2)+x(3) averages 15, satisfying the minimum requirementthat the sum of x and y be at least ten, and 6 g of2-hydroxy-2-methyl-1-phenylpropan-1-one, available commercially asDarocur™ 1173 from Radcure of Smyrna, Ga. The mixture was flow coatedonto polyethylene terephthalate film. After 5 minutes of drying in airthe coated film was subjected to curing by exposure to ultravioletradiation by two passes through a Fusion System processor two inchesfrom the 300 Watts per square inch (W/in²) Fusion-H lamps, at aprocessing speed of 30 feet per minute (fpm). The cured coating was 20microns thick and had a fogging time of 15 seconds with a delta Taberhaze of 10%.

While the oxyalkylene bridge groups in this particular diacrylate arenot 10 repeat units long, x=5, there are fifteen of them present in themolecule, meeting the minimum requirement of at least ten. Thus, thisexample shows that as long as there are the requisite number ofrepeating ether groups, it is not required that they form one continuouschain of polyether groups. Thus more than one oxyalkylene moiety isallowable even if the stoichiometric subscript is less than ten as longas the sum of the stoichiometric subscripts is ten or greater.

EXAMPLE 4

A coating composition was prepared from the following ingredients:

1) 100 g of aqueous colloidal silica, having an average particle size of20±4 nanometers and 34 weight percent silica (component (A), Nalcoag1034A™);

2) 100 g of CH₂ ═CHC(O)O--(CH₂ CH₂ O)_(x) --OC(O)CH═CH₂, where xaverages approximately 13, available commercially as SR610™ fromSartomer of Exton, Pa.(component (B)); and

3) 12 g of 2-hydroxy-2-methyl-1-phenylpropan-1-one, availablecommercially as Darocur™ 1173 from Radcure of Smyrna, Ga. The resultingmixture was diluted with 50 g iso-propyl alcohol and coated onto apolycarbonate panel. After drying for 5 minutes in air, the coated panelwas subjected to ultraviolet radiation to cure the coating as describedin example 1. The cured coating had a thickness of 20 microns, a foggingtime of 25 seconds, and a delta Taber haze of 20%. By comparison, theTaber delta haze of the uncoated polycarbonate was 40%.

EXAMPLE 5

A coating composition was prepared from the following ingredients:

1) 20 g of aqueous colloidal silica, having an average particle size of20±4 nanometers and 34 weight percent silica (component (A), Noalcoag1034A™);

2) 20 g of CH₂ ═CHC(O)O--(CH₂)₆ --OC(O)CH═CH₂, hexanediol diacrylate(HDDA); and

3) 2.4 g of 2-hydroxy-2-methyl-1-phenylpropan-1-one, availablecommercially as Darocur™ 1173 from Radcure of Smyrna, Ga. The resultingmixture was diluted with 200 g iso-propyl alcohol and coated ontopolycarbonate (PC) panels and polyethylene terephthalate (PET) film.After ultraviolet curing, both the coated PC and the coated PET foggedimmediately when subjected to the fogging test. By reference to example1 and example 4, the presence of a di- or multi-functional alkylenecompound possessing at least one polyoxyalkylene divalent radical, e.g.CH₂ ═CHC(O)O--(CH₂ CH₂ O)_(x) --OC(O)CH═CH₂ (where x is on averageapproximately 13), renders the coating composition anti-fogging.

EXAMPLE 6

Several small batches were prepared where methacryloxypropyl trimethoxysilane was reacted with aqueous colloidal silica as follows to produce amixture of the reaction product or hydrolyzate (acrylate functional Tresin), hexanediol diacrylate and silica.

In an Erlenmyer flask equipped with a magnetic stirring bar was added121.7 g of iso-propyl alcohol, 86.9 g, Nalcoag 1034A™, aqueous colloidalsilica (34 weight percent silica) and 0.07 g 4-OH TEMPO. To this mixturewas added 13.0 g methacryloxypropyltrimethoxy silane. The mixture washeated to reflux, approximately 80° C., for two hours and was thencooled to room temperature. 36.2 g of hexanediol diacrylate and 325 giso-propyl alcohol was then added. This mixture was then vacuum strippedat 10-20 torr on a rotary evaporator until no more overhead wascollected. Seventy-five grams of material was recovered that had acomposition as follows: silica (29.5 g), hexanediol diacrylate (36.2 g),and 9.4 g methacyloxypropyl silsesquioxane. This composition is reportedin Table 1 broken down by its constituents, silica, 1,6 hexanedioldiacrylate, and acrylate functional T resin (in this casemethacryloxypropyl silsesquioxane; it is to be noted thatmethacryloxypropyl silsesquioxane is the hydrolysis and polycondensationproduct of methacryloxypropyl tri-methoxy silane).

                  TABLE 1                                                         ______________________________________                                        Anti-Fog Coating Compositions Containing Acrylate Polyethers,                 Finely Divided Silica, and an Acrylate Functional T Resin                                       1,6-                                                                          Hexanediol        Acrylate                                                    diacrylate                                                                              SR610.sup.2 or                                                                        Functional T                                       Silica.sup.1,                                                                          (HDDA),   SR295.sup.3                                                                           Resin.sup.4                               Formulation                                                                            wt. %    wt. %     wt. %   wt. %                                     ______________________________________                                        A        31       37        23.sup.3                                                                              9                                         B        27       32        33.sup.2                                                                              8                                         C        20       24        50.sup.2                                                                              6                                         D        16       19        60.sup.3                                                                              5                                         E        13       16        67.sup.2                                                                              4                                         F        10       12        75.sup.2                                                                              3                                         G        8        10        80.sup.2                                                                              2                                         H        7        8         83.sup.2                                                                              2                                         ______________________________________                                         Notes to Table 1:                                                             .sup.1. Weight percent silica is from an aqueous dispersion of colloidal      silica, Nalcoag 1034A ™, which is 34 weight percent silica.                .sup.2. SR610 ™ is CH.sub.2CHC(O)O(CH.sub.2 CH.sub.2                       O).sub.xOC(O)CHCH.sub.2, where x averages approximately 13.                   .sup.3. SR295 ™ is pentaerythritoltetraacrylate.                           .sup.4. Defined as the reaction product of methacryloxy propyl trimethoxy     silane and water in the presence of an effective amount of a hydrolysis       and condensation catalyst.                                               

To 100 parts by weight of each of the compositions listed in Table 1were added 6 parts by weight of 2-hydroxy-2-methyl-1-phenylpropan-1-one,available commercially as Darocur™ 1173 from Radcure of Smyrna, Ga. andan additional 200 parts by weight of iso-propyl alcohol. Polycarbonatepanels were flow coated and allowed to air dry for 2-5 minutes prior tocuring with ultraviolet radiation, one pass under two 300 W/in² Fusion Hlamps at a speed of 20 fpm.

                  TABLE 2                                                         ______________________________________                                        Performance Properties of Anti-Fog Coating Compositions                       Containing Acrylate Polyethers, Finely Divided Silica, and an Acrylate        Functional T Resin                                                                          Fogging Time,                                                                            Delta Taber Haze                                     Formulation   seconds    (100 cycles), % change                               ______________________________________                                        A             2          n/a                                                  B             3          6                                                    C             5          8                                                    D             2          n/a                                                  E             9          15                                                   F             13         15                                                   G             14         22                                                   H             15         29                                                   uncoated polycarbonate                                                                      1          38                                                   ______________________________________                                    

These results show marked improvement by most of the formulations infogging time. Additionally, some of these compositions also showimproved abrasion resistance, lower delta Taber haze (% change). Theseresults demonstrate that good abrasion resistance can be combinedsimultaneously with anti-fogging properties.

Having described the invention, that which is claimed is:
 1. Anultraviolet curable hardcoat composition comprising:(A) finely dividedsilica: (B) a multi-functional compound containing two or more terminalacrylic moieties and one or more divalent oxyalkylene radicals havingthe formula:

    --((CX.sub.2).sub.n O).sub.x ((CX.sub.2).sub.m O).sub.y --

where the sum of the x stoichiometric subscripts for each divalentoxyalkylene radical and the sum of the y stoichiometric subscripts foreach divalent oxyalkylene radical when said sums are added together isten or greater and the stoichiometric subscripts n and m are differentand have values independently ranging from one to ten, where each X isindependently selected from the group consisting of hydrogen, one toforty carbon atom monovalent hydrocarbon radicals and six to fortycarbon atom monovalent aromatic hydrocarbon radicals; and (C) anolefinically functionalized trialkoxy silane.
 2. The composition ofclaim 1 wherein the multi-functional olefin contains one divalentoxyalkylene radical.
 3. The composition of claim 2 wherein X is hydrogenor methyl.
 4. The composition of claim 3 wherein X is hydrogen.
 5. Thecomposition of claim 4 wherein the multi-functional olefin has theformula: ##STR11##
 6. The composition of claim 5 wherein m is 0, y is 0,n is 2 and x is
 13. 7. The composition of claim 6 wherein the finelydivided silica is aqueous colloidal silica.
 8. The composition of claim7 wherein the olefinically functionalized trialkoxy silane has theformula: R⁴ Si(OR³)₃, where R⁴ is a monovalent alkylene radical havingfrom two to forty carbon atoms and R³ is selected from the group of oneto forty carbon atom monovalent alkyl hydrocarbon radicals and six toforty carbon atom monovalent aromatic hydrocarbon radicals.
 9. Thecomposition of claim 8 wherein the olefinically functionalized trialkoxysilane is methacryloxypropyl trimethoxy silane.
 10. The curedcomposition of claim
 1. 11. An ultraviolet curable hardcoat compositioncomprising the reaction product of:(A) finely divided silica; (B) amulti-functional olefin compound containing two or more terminal acrylicmoieties and one or more divalent oxyalkylene radicals having theformula:

    --((CX.sub.2).sub.n O).sub.x ((CX.sub.2).sub.m O).sub.y --

where the sum of the x stoichiometric subscripts for each divalentoxyalkylene radical and the sum of the y stoichiometric subscripts foreach divalent oxyalkylene radical when said sums are added together isten or greater and the stoichiometric subscripts n and m are differentand have values independently ranging from one to ten, where each X isindependently selected from the group consisting of hydrogen, one toforty carbon atom monovalent hydrocarbon radicals and six to fortycarbon atom monovalent aromatic hydrocarbon radicals; and (C) anolefinically functionalized trialkoxy silane; and (D) a hydroxylicsolvent.
 12. An ultraviolet curable hardcoat composition consistingessentially of:(A) finely divided silica: (B) a multi-functional olefincompound containing two or more terminal acrylic moieties and one ormore divalent oxyalkylene radicals having the formula:

    --((CX.sub.2).sub.n O).sub.x ((CX.sub.2).sub.m O).sub.y --

where the sum of the x stoichiometric subscripts for each divalentoxyalkylene radical and the sum of the y stoichiometric subscripts foreach divalent oxyalkylene radical when said sums are added together isten or greater and the stoichiometric subscripts n and m are differentand have values independently ranging from one to ten, where each X isindependently selected from the group consisting of hydrogen, one toforty carbon atom monovalent hydrocarbon radicals and six to fortycarbon atom monovalent aromatic hydrocarbon radicals; and (C) anolefinically functionalized trialkoxy silane.
 13. A method for making anultraviolet curable hardcoat composition comprising:(a) reacting(i) anolefinically functionalized trialkoxy silane with (ii) a finely dividedsilica in the presence of (iii) a hydroxylic solvent to produce areaction product and (b) mixing the reaction product with amulti-functional olefin compound containing two or more terminal acrylicmoieties and one or more divalent oxyalkylene radicals having theformula:

    --((CX.sub.2).sub.n O).sub.x ((CX.sub.2).sub.m O).sub.y --

where the sum of the x stoichiometric subscripts for each divalentoxyalkylene radical and the sum of the y stoichiometric subscripts foreach divalent oxyalkylene radical when said sums are added together isten or greater and the stoichiometric subscripts n and m are differentand have values independently ranging from one to ten, where each X isindependently selected from the group consisting of hydrogen, one toforty carbon atom monovalent hydrocarbon radicals and six to fortycarbon atom monovalent aromatic hydrocarbon radicals.
 14. Thecomposition of claim 1 wherein the multi-functional olefin compoundcontains more than one divalent oxyalkylene radical.
 15. The compositionof claim 14 wherein the multi-functional olefin compound has theformula: ##STR12## where x averages
 5. 16. The cured composition ofclaim 15.